NEW YORK (Reuters Health) - Beyond making teens sleepy
during the day, staying up late may be raising their blood
pressure, setting them up for later heart troubles, say Chinese
researchers.

"Sleep is an essential part of everyone's life. However,
with continuous advancement of technology, the portion of sleep
in each day is diminishing," the study's lead author Chun-Ting
Au told Reuters Health in an email.

Au is a research associate in the Department of Pediatrics
at the Faculty of Medicine of the Chinese University of Hong
Kong.

He and his team wanted to examine the relationship between
sleep and blood pressure in teens without other potential causes
of high blood pressure, such as obesity or sleep apnea.

"Scientifically, as the association between sleep duration
and blood pressure was still uncertain, we decided to conduct
this study to examine the association in a more precise way," Au
said.

The researchers invited adolescents who had participated in
a previous study on obstructive sleep apnea. All participants in
the new study were healthy and not overweight or obese for their
ages, and none had sleep apnea or recent surgery involving the
airways.

A total of 143 kids between the ages of 10 and 18 completed
the study. The kids filled out sleep diaries for seven days
before they entered a sleep lab for 24-hour sleep studies, where
they were monitored for blood pressure, sleep duration and the
quality of their sleep.

In general, the children who had less total sleep during the
week had slightly higher blood pressure measurements. On
average, each hour of nightly lost sleep was associated with an
increase of 2 mm Hg in systolic blood pressure (the top number)
and 1 mm Hg in diastolic blood pressure.

The study did not prove that short sleep duration would
cause high blood pressure in adolescents. Some other cause could
be behind both the higher blood pressure readings and reduced
sleep times.

The researchers point out that previous studies have found
that kids with short sleep times had higher levels of the stress
hormone cortisol in the morning, and that sleep deprivation may
blunt the ability of blood vessels to respond to changes in
pressure.

In the current study, researchers also found that kids who
got the least amount of sleep based on their sleep diaries
generally had later bedtimes and woke up earlier every day. But
during the 24-hour sleep study, those kids fell asleep sooner
and had longer total sleep times than the rest of the kids.

This change in sleep patterns might signal a rebound from
sleep deprivation in the preceding week and suggests that kids
might be able to make up for some lost sleep, Au's team writes
in the journal Pediatrics.

"Our results found that blood pressure was sensitive to
changes in sleep pattern, implicating that having longer sleep
may have beneficial effects on blood pressure and thus
cardiovascular health," Au said.

"On the other hand, although blood pressure was more closely
associated with the sleep time on the night before, the
carryover effect of the 'sleep debt' accumulated over the past
few days remained significant," he said.

"This suggests that occasional adequate sleep, as what we
commonly do during weekends, may improve the situation a little
bit, but does not completely reverse the detrimental effects of
long-term sleep deprivation on blood pressure," Au said.

Dr. Judith Owens, director of Sleep Medicine at the
Children's National Medical Center in Washington, DC, said
there's not much published research in this area.

"As the authors point out, a lot of what's been done
previously was confounded by this issue of obesity and
obstructive sleep apnea. I think this was a very important and
innovative step to eliminate those confounding variables, and
look at this issue in otherwise healthy adolescents," she told
Reuters Health.

Owens, a professor of Pediatrics at George Washington
University School of Medicine and Health Sciences, was not
involved in the new study.

She said this is an issue that affects all teenagers, not
just kids who have sleep problems.

"This is something that goes on for at least 9 months of the
year, for years, for the average adolescent, so the implication
that this may have measurable cardiovascular effects is so
important," Owens said.

Owens also said she hopes reports like this lead to
long-term studies following sleep-deprived teens into their
adult years.

"If we can see these short term kinds of effects, maybe
we'll see more funding to do these very expensive studies where
we're measuring these same kinds of issues in adults who were
adolescents undergoing this sleep deprivation," she said.

Owens also told Reuters Health that disruptions in circadian
rhythms might also contribute to cardiovascular risk.

Adolescents are often sleep deprived during the school year
because their circadian rhythms don't match up with school
schedules and they often can't fall asleep early enough to meet
their sleep needs.

Au says parents can help their kids get the sleep they need.

"Be consistent and perseverant," he wrote in an email.
"There are several techniques (e.g. developing a nightly bedtime
routine) that can help children establish a regular sleep
pattern. You may easily obtain a list of them from the Internet.
No matter what technique you use, consistency and perseverance
is the key to success."